R in Action

Chapter 9. Analysis of variance

 

This chapter covers

• Using R to model basic experimental designs
• Fitting and interpreting ANOVA type models
• Evaluating model assumptions

 

In chapter 7, we looked at regression models for predicting a quantitative response variable from quantitative predictor variables. But there’s no reason that we couldn’t have included nominal or ordinal factors as predictors as well. When factors are included as explanatory variables, our focus usually shifts from prediction to understanding group differences, and the methodology is referred to as analysis of variance (ANOVA). ANOVA methodology is used to analyze a wide variety of experimental and quasi-experimental designs. This chapter provides an overview of R functions ...